Embodiments of the present invention relate to process kit components for a titanium sputtering chamber.
In the manufacture of integrated circuits and displays, a substrate, such as a semiconductor wafer or display panel, is placed in a process chamber and processing conditions are set in the chamber to deposit or etch material on the substrate. A typical chamber comprises an enclosure wall that encloses a plasma zone, a gas supply to provide a process gas in the chamber, a gas energizer to energize gas to process the substrate, a substrate support to support a substrate, and a gas exhaust to maintain a gas pressure in the chamber. Such chambers can include, for example, sputtering or PVD, CVD, and etching chambers. In a magnetron PVD sputtering chambers, a target is sputtered in a magnetic field causing sputtered target material to deposit on a substrate facing the target. In the sputtering process, a process gas comprising an inert or reactive gas is supplied into the chamber, and the target is electrically biased while the substrate maintained at an electrical floating potential to generate charged plasma species in the chamber which sputter the target.
In one type of process, a sputtering chamber is used to deposit a layer comprising titanium or a titanium compound on a substrate for a variety of applications. For example, a sputtered titanium layer can be used as a barrier layer to inhibit the diffusion of an overlying material into the layers below the barrier layer. The titanium layers can be used by themselves, or in combination with other layers, for example, Ti/TiN stacked layers are often used as liner barrier layers, and to provide contacts to the source and drain of a transistor. In another example, a titanium layer is deposited on a silicon wafer and portions of the titanium layer in contact with the silicon are converted to titanium silicide layers by annealing. In another configuration, the diffusion barrier layer below a metal conductor, includes a titanium oxide layer formed by sputter depositing titanium on the substrate and then transferring the substrate to an oxidizing chamber to oxidize the titanium by heating it in an oxygen environment to form titanium oxide. Titanium oxide can also be deposited by introducing oxygen gas into the chamber while titanium is being sputtered. Similarly, titanium nitride can be deposited by reactive sputtering methods by introducing a nitrogen containing gas into the chamber while sputtering titanium.
Conventional sputtering targets which are shaped as right-cylinders have several problems when used for titanium sputtering. One problem arises because titanium material sputtered from the vertical sidewalls of such a target accumulate on adjacent surfaces of the chamber. The accumulated sputtered material eventually flakes off with process heating/cooling cycles to fall upon and contaminate the substrate. Also, in certain chambers, a dielectric isolator ring is located adjacent to the target to isolate the electrical potential applied to the target from the potential applied to the chamber walls and/or support. However, the sputtered titanium material accumulating on the dielectric isolator eventually forms a continuous film that can cause electrical shorts between the chamber walls and target. Another problem arises because conventional targets made by bonding a sputtering material plate onto a stainless steel backing plate, often debond from the backing plate due to thermal expansion stresses. Thus, it is desirable to have a sputtering target that provides reduced sidewall sputtering and which does not easily debond.
The sputtering chamber also includes a process kit comprising components arranged about the substrate support and chamber sidewalls to receive sputtering deposits which would otherwise accumulate on the side surfaces of the support or on the backside surface of the substrate. The process kit can include, for example, a deposition ring, cover ring, and shadow ring, located about the periphery of the substrate. The process kit can also include shields and liners which serve as a receiving surface to receive sputtering deposits which would otherwise deposit on the sidewalls of the chamber. The process kit components also reduce erosion of the internal chamber structures by the energized plasma. The components are also often designed to be easily removable for cleaning of accumulated deposits.
However, conventional process kit components often do not allow sufficient amounts of sputtered deposits to accumulate thereon. The process deposits often flake off due to thermal stresses and contaminate the substrate after a limited number of process cycles. Increasing the amount of sputtered deposits that can accumulate on these components allows a greater number of substrates to be sequentially processed in the chamber without shutting down the chamber to dismantle the components for cleaning them. Each time the chamber requires cleaning, the resultant downtime of the chamber increases the cost of processing substrates. Thus it is desirable to have process chamber components that maximize the amount of time the chamber can be operated without shutting down the chamber, especially for titanium sputtering processes. Also, the chamber components should be able to receive sputtered deposits without causing the components to stick to one another or to other components which can result in damage to the substrate or components when they are attempted to be removed from the support.
Thus it is desirable to have a sputtering target that limits the formation and deposition of sputtered material from its sidewalls on adjacent chamber surfaces. It is further desirable to have process kit components that minimize chamber down time so that the chamber can be operated to sputter deposit material on a greater number of substrates without shutting down the chamber to clean the components. It is further desirable to have process kit components that can allow deposits to accumulate on their surfaces without causing sticking of the components to each other or to the substrate.